Abaixo está uma instrução que descreve uma tarefa de geração de SQL, combinada com uma entrada que fornece mais contexto sobre os esquemas de tabela disponíveis. Escreva o código SQL que responda adequadamente à solicitação
 ###Instrução: Quantas etapas existem?
 ###Tabelas: CREATE TABLE 1962 (1962_id AUTO_INCREMENT PRIMARY KEY, meas. num. INT, passed VARCHAR, YES votes INT, NO votes INT, % YES VARCHAR, Const. Amd.? VARCHAR, type VARCHAR, description VARCHAR) CREATE TABLE classification_leadership (classification_leadership_id AUTO_INCREMENT PRIMARY KEY, Stage INT, Winner VARCHAR, General classification VARCHAR, Sprint Classification VARCHAR, Mountains Classification VARCHAR, Points Classification VARCHAR, Team Classification VARCHAR) CREATE TABLE louisiana_parishes_ranked_by_per_capita_income (louisiana_parishes_ranked_by_per_capita_income_id AUTO_INCREMENT PRIMARY KEY, Parish VARCHAR, Per capita income VARCHAR, Median household income VARCHAR, Median family income VARCHAR, Population INT, Number of households INT) CREATE TABLE itf_singles_finals_6–1 (itf_singles_finals_6–1_id AUTO_INCREMENT PRIMARY KEY, Outcome VARCHAR, Date VARCHAR, Tournament VARCHAR, Surface VARCHAR, Opponent in Final VARCHAR, Score in Final VARCHAR) CREATE TABLE top_8_teams_qualified_for_team_finals (top_8_teams_qualified_for_team_finals_id AUTO_INCREMENT PRIMARY KEY, Position VARCHAR, Country VARCHAR, Floor VARCHAR, Pommel Horse VARCHAR, Rings VARCHAR, Vault VARCHAR, Parallel Bars VARCHAR, Horizontal Bar VARCHAR, Team Total VARCHAR)  
SELECT MAX Stage FROM classification_leadership